At the present time, transmission of information via the Internet, whether digital data, digital audio, digital video, or other forms of data signals, is vital to the world's business.
These signals are carried by twisted-pair cable, coaxial cable, filter optic cable, or by wireless radio or satellite communication links. These channels may be narrow-band or wide-band. In addition to the Internet, there are many other forms of electronics communication channels, both analog and digital.
For many applications, there is need for two-way simultaneous communication. Currently, this is done by separating the inbound and outbound signals by placing them in different frequency bands. In order to conserve bandwidth and increase channel capacity, this invention provides means for two-way transmission of information signals in the same channel, in the same frequency band, at the same time.
Bi-directional amplification and communication systems have been proposed in the prior art. Separating inbound and outbound signals by placing them in separate frequency bands is commonly done (see for example U.S. Pat. No. 5,365,368). Separation of inbound and outbound signals by transmitting them at mutually exclusive times for radar and television applications is taught by U.S. Pat. Nos. 5,105,166 and 4,714,959. In microwave radio systems, separation can be achieved by utilizing horizontal and vertical polarizations for inbound and outbound radiation (see U.S. Pat. No. 5,481,223). This approach is workable, except for transmission through multipath where horizontal and vertical polarization components would become mixed. A different approach is taken by U.S. Pat. No. 5,119,365, which shows means for cancellation of transmitted signal components that leak into the received signal path at the head end of a bi-directional wire or cable communication line. Further along this direction, U.S. Pat. No. 5,187,803 shows a means for cancellation of transmitted signal components that leak into the received signal path within a bi-directional amplifier located in the middle of a two-way wire or cable communication line. The problem with the prior-art cancellation methods is that they depend critically on analog circuits whose component values must be adjusted, tuned, and balanced to create cancellation. There is no automatic means for initial tuning or for maintaining balance over time in the presence of line and component impedance changes, generally due to temperature changes and ageing.
Limitations of the prior art are overcome by the methods of this invention. Inbound and outbound signals are separated by means of cancellation techniques, which are based on adaptive filtering. Learning and self-adaptive circuits are used in combinations to make initial tuning for cancellation automatic, and to continually and automatically maintain the circuit balance necessary for separation of inbound and outbound signals.